1. Field of Invention
The invention relates to a transducer for converting at least one input signal fed to a first input into a corresponding electric output signal, which can be output via at least one first output, wherein the input signal can be processed via an analog transmission path into an analog transducer signal.
2. Description of Related Art
Transducers for generating analog transducer signals have been known for a long time and serve the purpose of detecting a sensor signal as an input signal coming from a sensor element and converting the detected signal into a normally standardized signal as electric output signal, so that the output signal, for example, can be used by higher-level process control.
The term transducer is not to be understood as limiting in any way. For example, the physical variables of the signal input to and the signal output from the transducer can be the same or can be different. Typically, however, the input signal also is an electric signal. Although the electric input signal can be actively provided by a sensor element connected at an input of the transducer, the connected sensor element also can be fed with energy from the transducer, so that the actual electric input signal results through such interaction. It is common for transducers to have the output designed as a current interface, in which the dimensions of the detected measured value to be transmitted are encoded by currents ranging from 4 mA to 20 mA, and the like. This is particularly common in so-called two-wire devices that receive their energy supply via such a current interface.
If it is said that the sensor-side input signal can be processed into an analog converter signal via an “analog transmission path,” then a circuit-type implementation of the transmission path is kept in an analog form, in which the conversion of the input signal to the analog converter signal is done without temporal and/or value-based quantized intermediate steps in the sense of digital technology. Such circuit-type implementation can occur in a discrete as well as integrated form. As an analog transmission path, such circuits are taken into consideration, which have digital components in terms of circuit technology. However, such digital components are not switched intermediately to the analog transmission path of the input signal into an analog converter signal, but rather serve, for example, only to parameterize the analog circuit. Such purely analog implemented transmission paths in this sense have the advantage that they are very fast due to the technology used, wherein the analog converter signal follows the varying input signal practically without delay.
Transducers may also have a digital transmission path in place of an analog transmission path, in which the input signal is converted in terms of circuits into a digital converter signal using digital means (i.e., using temporal and/or value-based quantization). Usually simple microcontrollers are used for implementation of such digital transmission paths, which already have the required functional abilities and interfaces for signal processing, for example, such as multiplexers, digital/analog converters, analog/digital converters, programmable boosters, programmable current outputs, serial interfaces, and the like.
The reaction times of digitally implemented transducers or of transducers having a digital transmission path are exceptionally large compared to the reaction times of analog transmission paths. For example, the reaction times of such transducers can be much greater than the maximum permitted dead times in security related applications, in particular when detecting quickly-changing process variables. The advantage of transducers having digital transmission paths is that a considerably higher accuracy in converting the input signal into a converter signal can be achieved using such circuits than is possible in the implementation of the transmission path with analog circuit technology.
Regardless of which type of transducer is used to solve a measuring task, it is required in security related applications to provide redundant back-up systems. Such redundancies are then normally produced using multiple parallel transducers, which results in relatively higher costs, a technically elaborate design, and which does not resolve the conflict between analog or digitally implemented circuit variations.